"Bismarck was so motivated to donate and help Dr. Garcia that he actually agreed to enter a paired exchange," revealed Dr. Sahajpal.

A paired exchanged is a complex transplant process that works like a chain. Basically, donors agree to give their organ to a stranger in exchange for a match for their friend or loved one.

"It's like a domino effect," Dr. Garcia explained.

The chains are connected through a transplant database and can include several pairs, which was the case for Dr. Garcia and Siero.

Dr. Moises Garcia (left) and Dr. Ajay Sahajpal (right)

"There were eight people involved -- four donors and four recipients of the chain," Dr. Sahajpal said.

In March, Siero donated his kidney to someone he didn't know. In return, Dr. Garcia received his new kidney.

"A big one actually," laughed Dr. Garcia.

Bismarck Siero (left) and Dr. Moises Garcia (right)

Now, he's ready to get back to seeing patients -- grateful for Siero and each person in his donor chain.

"We are family together," Dr. Garcia said about all those involved.

Dr. Garcia has not returned to work yet, but hopes to soon. Siero is back in Nicaragua where he runs a non-profit, Sielo, that provides education and services for families of children with disabilities.

If you're not an organ donor and want to sign up, you can do it online by clicking HERE. You can also register to become an organ donor at the DMV.

If you're interested in learning more about living organ donation, click HERE.